This invention relates to a pneumatic device for handling yarns and more specifically, to such devices for handling yarn at high speeds.
French Pat. No. 2,086,991 and U.S. Pat. Nos. 2,677,964, 3,094,262 and 3,156,395 are illustrative of prior art pneumatic devices utilized for yarn handling; however, the pneumatic devices of these patents have the disadvantages of not operating satisfactorily when used for yarn moving at speeds of 2,000 meters per minute. The primary reasons for the failure of these pneumatic devices to properly handle yarn moving at high speeds are that the devices either exert insufficient traction on the yarn as it is moving through the device or they do not provided adequate suction to grip the yarn. Furthermore, the prior art devices normally operate with high air outputs and pressure which render them expensive to manufacture and difficult to manage while still failing to provide the required performance.
The device described in the French Pat. No. 2,086,991 allows yarns moving at higher speeds to be caught, for example at more than 20 m/sec, but only when this yarn is under low tension, for instance while sent to a waste collector during some handling on the spinning machine. However, such a device does not make it possible to catch a yarn moving forward at high speed while being under high tension as is the cause in a process integrating the spinning and drawing of yarns placed just before the taking-up position during the spinning-drawing operation. Particularly, when a take-up bobbin is completed, it is not possible to catch the yarn during high speed spinning with one of the prior art devices for deposing it on the new empty bobbin. It is then necessary to cut the yarn above the take-up position and to send it to a waste nozzle during doffing. When the new empty bobbin is in position, the yarn is again taken by the handling device at the waste nozzle inlet and run through the guides placed above the winder before it is laid on the empty bobbin.
It is also known according to French Pat. No. 1,487,627 to use a filament driving device comprising a tube provided with a slot having knives and pierced with jets for feeding air coming from a jacket slantwise towards a nozzle axis. However, such a nozzle is noisy, requires space and is not efficient, because the air jet kinetic energy cannot be properly used, the yarn can only be inserted into the nozzle by a depression created which impedes high speed air circulation and finally, the yarn length subjected to this depression is limited to the slot length. Consequently, the fluid feed needed is very high and that the nozzle cannot catch a yarn under tension at high speed.